Pressure Changes Within the Sac of Human Cerebral Aneurysms in Response to Artificially Induced Transient Increases in Systemic Blood Pressure

Abstract

C erebral aneurysms (CA) are vascular out-pouches that most commonly occur at the branching sites of cerebral arteries, usually around the Circle of Willis. Up to 5% of the world's population is estimated to harbor CA.1 Although most CA go unnoticed, initial symptoms are usually caused by sudden rupture, causing subarachnoid hemorrhage (SAH). SAH can be devastating; half of those with SAH die within a year, 2,3 and perhaps only ≈10% of survivors are functionally and neurocognitively normal. [4][5][6] Given these outcomes, recent interest has focused less on the treatment of SAH and more on prevention of hemorrhage.A fundamental step in tackling the broad problem of SAH is to understand the determinants of CA formation and rupture. In a study comparing the prevalence of hypertension in 20 767 Medicare patients with unruptured CA to a random sample of the hospitalized Medicare patients, hypertension was found in 43.2% of patients with unruptured CA compared with 34.4% in the comparison group.7 Hypertension was also found to be an independent risk factor for future aneurysm rupture in patients with unruptured aneurysms (risk ratio, 1.46; 95% confidence interval, 1.01-2.11).7 Thus, current thinking is that chronic hypertension is a strong modifiable risk factor for both CA formation and subsequent (and often deadly) rupture.It has long been speculated that an acute increase in systemic arterial pressure is the ictus that results in an increase in intra-aneurysm blood pressure, an increase in aneurysm wall tension, and rupture. However, the relationship between an acute increase in systemic blood pressure and intra-aneurysm pressure has not been studied directly. If acute increases in systemic blood pressure result in equivalent increases within the aneurysm, then patients with known unruptured aneurysms (1) might be reasonably advised to avoid activities that increase blood pressure (eg, exercise, sex); (2) be pretreated with antihypertensive agents before such activities; and (3) consider treatment of the aneurysm to prevent future aneurysm rupture during surges of blood pressure. Alternatively, if acute increases in systemic blood pressure do not result in equivalent changes within the aneurysm, acute transient hypertension per se may not greatly increase the likelihood of aneurysm rupture.Abstract-Formation and rupture of cerebral aneurysms have been associated with chronic hypertension. The effect of transient increase in blood pressure and its effect on intra-aneurysmal hemodynamics have not been studied. We examined the effects of controlled increases in blood pressure on different pressure parameters inside the sac of human cerebral aneurysms and corresponding parent arteries using invasive technology. Twelve patients (10 female, 2 male, age 54±15 years) with unruptured cerebral aneurysms undergoing endovascular coiling were recruited. Dual-sensor microwires with the capacity to simultaneously measure flow velocity and pressure were used to measure systolic, diastolic, and mean pressure inside the aneurysm sa...

Wpływ propofolu na prędkość przepływu krwi w tętnicy środkowej mózgu (VMCA) u chorych z niepękniętym tętniakiem wewnątrzczaszkowym podczas indukcji znieczulenia ogólnego

“…UIAs were found to have no impact on autoregulation of cerebral circulation [25]. Endovascular treatment of UIAs leads to ipsilateral impairment of carbon dioxide reactivity of the cerebral vessels [26]. Moreover, our observations reveal that the presence of UIA does not affect bilateral V MCA , which is consistent with the findings reported in the literature [25,27].…”

Evidence That a Subset of Aneurysms Less Than 7 mm Warrant Treatment

“…They found that a smaller angle was associated with increased rupture rate, a finding consistent with previous studies that showed increased wall shear stress when the angle of bifurcation decreases . Hasan and colleagues directly measured the pressure changes between the aneurysm and the systemic circulation . Dual‐sensor microwires with the capacity to simultaneously measure flow velocity and pressure were used to measure systolic, diastolic, and mean pressure inside the aneurysm sac and to measure both pressures and flow velocities in the feeder vessel just outside the aneurysm in patients undergoing endovascular treatment.…”

“…This could be possibly attributable to the fact that velocity alone cannot explain the rupture mechanism, since low‐flow velocity may lead to the opposite outcome, which is aneurysm thrombosis . Another reason would be that mean and peak flow velocities do not significantly change …”

Characteristics of Unruptured Compared to Ruptured Intracranial Aneurysms: A Multicenter Case–Control Study

“…A previous study has found a linear relationship between increase in systemic arterial pressure and pressure in the aneurysm sac 43 . This finding supports the hypothesis that a rapid increase in blood pressure rather than a chronic increased blood pressure lead to aneurysm rupture.…”